VMP Performance tests Heatshield Products’ I-M Shield on its GT350
By Steve Turner
Photos by Steve Turner and courtesy of Heatshield Products
As the factory continues to squeeze more and more performance out of its vehicles the software in the PCM is also quick to reel in the ignition timing in response to heat. Since heat can lead to detonation, this is a wise safeguard. However, for those of us that want maximum performance at all times, keeping the inlet air cooler and the timing more aggressive is a great idea.
Highly tuned modern performance cars are sensitive to increases in inlet air temperature, so we were intrigued to see Justin Starkey of VMP Performance test Heatshield Products I-M Shield on its Shelby GT350 project car.
During The Roar Before testing preceding the Rolex 24 Hours at Daytona we noted that the Shelby GT350R-C racers featured heat shield material on their airboxes and inlet tubes. That indicated to us that these cars might be sensitive to hot inlet air in extreme situations. When Heatshield Products said it would be testing its I-M Shield intake manifold kit at VMP Performance, we joined in to watch VMP’s Justin Starkey test the product on the company Shelby GT350 project car.
“We see a fair amount of sensitivity to inlet air temps, on both naturally aspirated and supercharged applications,†Justin explained. “Anything you can do to keep things cooler is good.â€
Heatshield Products offers a variety of Mustang-specific I-M Shield kits, including the 2012-2013 Boss 302 (PN 140008; $56.97) kit seen in this shot, as well as kits for the 2011-2014 Mustang GT (PN 140007; $50.97) and 2011-2014 V6 Mustangs (PN 140009; $56.97). Since the GT350 is new there isn’t a dedicated kit yet, so we opted to use the company’s universal kit (PN 140004; $89.97).
In preparation for the installation of the I-M Shield, Justin made baseline runs at normal operating temperatures then he ran three back-to-back runs to heatsoak the engine compartment. Both sets of runs were performed with the hood down and no fans in front of the radiator. That is quite the opposite of how cars are usually tested on a static chassis dyno, as cars moving down the road will see more airflow than a fan can replicate.
You check out some of those runs right here…
While it is easy to install the adhesive-backed I-M shield, it does require removing and replacing your car’s intake manifold. However, after our recent Cobra Jet intake testing, the VMP crew has plenty of experience swapping intakes on the latest Shelby.
In both instances the runs with the I-M Shield in place showed lower inlet temps as measured at the top of the intake with an infrared thermometer (which is not pure science but a solid indicator that the intake was seeing less heat). The runs starting at normal operating temperatures were about 10 degrees cooler, while the heatsoaked runs were about 5 degrees cooler. The lower temp readings were a good sign, however, in both cases the I-M Shield runs produces more power across the pull, which was the better news.
“It made a little more power than I expected,†Justin said of the shielded intake.
Because of the shape of the GT350 manifold’s plenum Heatshield Products universal I-M Shield kit got the nod. Justin cleaned the manifold to ensure it was free of oil or other contaminants. Then he custom-cut the universal kit to cover the entire underside of the intake manifold.The concept of these I-M kits is to block much of the heat rising from the engine block’s valley as it will warm the underside of the intake manifold and transfer some of that heat to the incoming air. As we all know, cooler air is denser and allows an engine to make more power.This shot was taken between the stock and shielded runs. Justin made all the dyno runs with the hood down and no fans running in front of the car. The first runs were simple baseline runs. Then he heat-soaked the car with three back-to-back runs to create a worst-case scenario, as your car will never see 8,000 going down the road with out air flowing over the radiator and through the engine compartment.After each run Justin documented the temperature of the intake with an infrared thermometer. The difference in runs was significant between the baseline and the shielded intake, where the top of the intake was down about 10 degrees. For the heatsoaked tests the difference was less pronounced but the car still made a little more power in shielded form and the temps dropped about 5 degrees. It’s not pure science, but an indicator that the I-M Shield was working. What we really wanted to know was how the cooler intake would impact the GT350’s rear-wheel output.Starting the runs at standard operating temperature you can see there is a clear benefit to blocking heat rising from the valley to the bottom of the intake manifold with the IM-Shield. The peak-to-peak gains were 8.93 horsepower and 5.27 lb-ft of torque, but the gains are consistent throughout the pull.To test the worst-case scenario Justin tested the stock and shielded configurations by heatsoaking them with repeated hood-down, no-fan runs. As you can see the baseline power drops off significantly as the PCM pulls timing in response to the hotter inlet air. With the shield in place the GT350 still makes more power across the powerband with peak gains of 8.95 horsepower and 1.68 lb-ft of torque.Under normal and extreme conditions there are definite benefits to running the I-M Shield on a modern Mustang’s composite intake manifold. In both situations the shielded intake shows benefits throughout the pull, as you can see from this sampling of data.
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